The present invention relates to removable, adjustable pushrods designed especially for Harley Davidson Evolution.RTM. type motorcycle engines. The Evolution.RTM. engine is a two cylinder four stroke gasoline type motorcycle engine. Pushrods are rods which are used in the internal combustion components of a motorcycle engine. In a typical engine the pushrod is movably connected at one end to the rocker arm at the top of a typical motorcycle combustion engine at one end and movably connected at the other end to the hydraulic lifter within the tappet block. The pushrod is engageable at its bottom end with the hydraulic lifter. In a motorcycle engine such as the Evolution.RTM. type engine, mechanical power is transferred from the flywheel assembly to the pinion shaft and pinion gear to the cam shaft, which transfers mechanical power to the tappet roller and hydraulic lifter within the tappet block. Then the pushrod conveys power at its upper end to the rocker arm within the rocker box assembly at the top of the motorcycle engine.
In a typical Evolution.RTM. type motorcycle engine, there is a spatial gap between the bottom of the rocker arm assembly at the top of the engine, and the top of tappet block at the lower part of the engine.
The top of the pushrod is movably connected to the rocker arm, which is encased within the confines of the rocker box assembly. Furthermore, the lower end of the typical pushrod is movable within the confines of the tappet block, for engagement with the hydraulic lifter. Therefore, a significant portion of the pushrod at both the top and bottom end is unavailable for inspection and removal without first exhaustively removing the rocker box assembly from the cylinder head of the motorcycle engine. Although a portion of the pushrod assembly is exposed within the aforesaid spatial gap, the top and bottom portions within the rocker arm assembly and tappet block assembly are inaccessible.
The top of each pushrod extends approximately 1 inch into the rocker box assembly where the top is engageable with the rocker arms which open and close the valves of the engine and extends approximately 1 inch into tappet block at bottom end of pushrod.
Typical original equipment manufactured Evolution.RTM. motorcycle engines utilize four pushrods constructed of approximately 3/8 inch hollow tubing with 3/8 inch hardened steel balls at each end for engagement with the rocker arm and hydraulic lifter respectively. Therefore the technician working on the rocker arms can only extract the pushrods by moving the rocker arm assembly off of the cylinder head of the engine.
Therefore, there is a need to efficiently perform valve train services including cam removal and/or replacement, hydraulic lifter repair or replacement, and pushrod inspection and replacement and pushrod cover 0-ring replacement.
Because the typical pushrods are of one piece construction, they cannot be removed from the pushrod inspection tube covering. Removal of the rocker arm assembly also requires removal of gaskets and seals which further complicate repair.
Therefore, there is a long felt need for an adjustable length pushrod which can be shortened in size from the top and bottom for removal of the pushrod from the engine within the pre-existing open space between the bottom of the cylinder head and the top of the tappet block of the Evolution.RTM. type motorcycle engine.
Various patents have been developed wherein a steel ball is threadably connected to the top of a pushrod for small, minute adjustments of the top of the pushrod within the rocker arm. Inventions pertaining to internal combustion engines in general have been described in U.S. Pat. Nos. 1,118,686; 1,261,632; 1,378,111; 1,464,082; 2,053,743; 2,970,585; and 3,908,615. Although some of these patents provide for adjustability of the top of the pushrod with the ball at the top, these adjustments are for minute little adjustments after the cylinder head and rocker box assembly have been completely disassembled, which ordinarily takes about three hours labor plus tedious replacement of seals and gaskets. Therefore, there is a long felt need for a pushrod which can adjust in size and for easy and efficient removal within the open space between the bottom of the cylinder head of the engine and the top of the tappet block of the Evolution.RTM. type motorcycle engine.